package com.链表;

/**
 * 将两个有序链表合并为一个新的有序链表并返回。新链表是通过拼接给定的两个链表的所有节点组成的。
 * https://leetcode-cn.com/problems/merge-two-sorted-lists/
 */
public class 合并两个有序列表 {
    public static ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        if(l1 == null){
            return l2;
        }else if(l2 == null){
            return l1;
        }else if(l1.val < l2.val){
            l1.next =  mergeTwoLists(l1.next,l2);
            return  l1;
        }else {
            l2.next =  mergeTwoLists(l1,l2.next);
            return l2;
        }


    }
    public static  ListNode merge(ListNode l1,ListNode l2){
        ListNode prehead = new ListNode(-1);
        ListNode pre = prehead;
        while(l1 != null && l2 != null){
            if(l1.val < l2.val){
                pre.next = l1;
                l1 = l1.next;
            }else{
                pre.next = l2;
                l2 = l2.next;
        }
            pre = pre.next;
        }
        pre.next = l1 == null ? l2 : l1;
        return prehead.next;
    }
    public static void main(String[] args) {
         ListNode l1 = new ListNode(new int[]{1,2,3});
         ListNode l2 = new ListNode(new int[]{4,5,6});

        //System.out.println(mergeTwoLists(l1,l2));
        System.out.println(merge(l1,l2));
    }
}
